Using a nonlinear time varying tyre model, this paper simulatively analyzes the influence of road surface roughness amplitude and road spatial frequency on automobile ground adhesion ability. The result shows that wi...Using a nonlinear time varying tyre model, this paper simulatively analyzes the influence of road surface roughness amplitude and road spatial frequency on automobile ground adhesion ability. The result shows that with the increase of road surface roughness, the tyre adhesion ability declines, and the automotive braking distance increases. Moreover, the reliability of the nonlinear time varying tyre model in reflecting the influence of the road surface roughness is validated. It is testified that this model is an effective dynamic one in the simulation of automotive braking performance on uneven road.展开更多
After some tragic fire events,Directive 2004/54/EC was issued to ensure a minimum safety level for tunnels belonging to the Trans-European Road Network longer than 500 m.Nowadays,most of the Italian road tunnels are s...After some tragic fire events,Directive 2004/54/EC was issued to ensure a minimum safety level for tunnels belonging to the Trans-European Road Network longer than 500 m.Nowadays,most of the Italian road tunnels are still not in compliance with the minimum safety requirements,thus refurbishment works are often planned.By developing a traffic macro-simulation model,this paper aims at assessing the resilience of an existing twin-tube motorway tunnel when one of its tubes is partially or completely closed due to planned activities.Several scenarios were investigated,also considering the availability or not of an alternative itinerary in the surrounding transportation network.The average vehicles’speed was used as a functionality parameter,while the resilience metrics were the resilience loss,the recovery speed,and the resilience index.The findings showed higher resilience losses for complete closure rather than partial closure of the tube under planned refurbishment works.The implementation of digital technologies,such as variable message signs,might reduce the resilience loss of the tunnel system.This research might represent a reference for tunnel management agencies in the choice of the most appropriate traffic control strategy to improve tunnel resilience in the event of planned activities.展开更多
The phenomenological equations of motion for the international roughness index (IRI) have been reviewed and discussed in terms of Lagrangian method in physics. The current paper proposes a practical, two-dimensional m...The phenomenological equations of motion for the international roughness index (IRI) have been reviewed and discussed in terms of Lagrangian method in physics. The current paper proposes a practical, two-dimensional model for studying essentially three-dimensional, vibrating,?and?mechanical systems (vehicles). The purpose is to provide a new profiling method for IRI, which is practical in computations and compatible with traditional profiling for roughness of a road-surface. The modern technology employs elaborated sensors such as gyro sensor, Global Positioning System (GPS), magnetometer sensor,?and?accelerometer to measure high-speed longitudinal motions, resulting in time series of big-data expressed as compressed longitudinal spikes. The time series of longitudinal spikes obtained from high-speed longitudinal motions are traditionally considered as a background noise for constructing a profile. The conventional IRI is calculated from big-data of the road profile by employing statistical method, but the Lagrangian model dynamically determines the road profile. The useful concept and relation among the road-roughness function?, associated roughness index (ARI), acceleration and position are introduced and examined in the present paper. The associated roughness index (ARI) defined by the current dynamical approach is examined by applying virtual simulations which represent roughness of a road-surface. The current theoretical model supports and compensates information of interpreting a profile of IRI and elucidates physical meanings for the roughness index of a road-surface.展开更多
机电馈能悬挂系统是一种新型悬挂系统,在实现装甲车辆车身减振同时回收地面传递给车身的振动能量。根据摆臂式机电馈能悬挂系统工作原理,建立了相应数学物理模型,基于Adams和AMEsim搭建了减振系统与馈能系统联合仿真模型,分析了行星变...机电馈能悬挂系统是一种新型悬挂系统,在实现装甲车辆车身减振同时回收地面传递给车身的振动能量。根据摆臂式机电馈能悬挂系统工作原理,建立了相应数学物理模型,基于Adams和AMEsim搭建了减振系统与馈能系统联合仿真模型,分析了行星变速器传动比、电池电阻和扭转缓冲器刚度对系统阻尼特性和馈能性能的影响。结果表明:在车速为45 km/h的铺面路、戈壁路、起伏路、砂石路4种路面工况下,车身加速度均方根值平均为4.11 m/s 2,平均馈能功率为1411.57 W,机电馈能悬挂系统有良好的减振性能和可观的馈能功率;随着行星变速器传动比增大,悬挂系统阻尼力矩和馈能功率逐渐增大,且影响显著;随着电池电阻增加,阻尼力矩和馈能功率逐渐降低;扭转缓冲器刚度变化对悬挂系统性能影响较小。展开更多
文摘Using a nonlinear time varying tyre model, this paper simulatively analyzes the influence of road surface roughness amplitude and road spatial frequency on automobile ground adhesion ability. The result shows that with the increase of road surface roughness, the tyre adhesion ability declines, and the automotive braking distance increases. Moreover, the reliability of the nonlinear time varying tyre model in reflecting the influence of the road surface roughness is validated. It is testified that this model is an effective dynamic one in the simulation of automotive braking performance on uneven road.
文摘After some tragic fire events,Directive 2004/54/EC was issued to ensure a minimum safety level for tunnels belonging to the Trans-European Road Network longer than 500 m.Nowadays,most of the Italian road tunnels are still not in compliance with the minimum safety requirements,thus refurbishment works are often planned.By developing a traffic macro-simulation model,this paper aims at assessing the resilience of an existing twin-tube motorway tunnel when one of its tubes is partially or completely closed due to planned activities.Several scenarios were investigated,also considering the availability or not of an alternative itinerary in the surrounding transportation network.The average vehicles’speed was used as a functionality parameter,while the resilience metrics were the resilience loss,the recovery speed,and the resilience index.The findings showed higher resilience losses for complete closure rather than partial closure of the tube under planned refurbishment works.The implementation of digital technologies,such as variable message signs,might reduce the resilience loss of the tunnel system.This research might represent a reference for tunnel management agencies in the choice of the most appropriate traffic control strategy to improve tunnel resilience in the event of planned activities.
文摘The phenomenological equations of motion for the international roughness index (IRI) have been reviewed and discussed in terms of Lagrangian method in physics. The current paper proposes a practical, two-dimensional model for studying essentially three-dimensional, vibrating,?and?mechanical systems (vehicles). The purpose is to provide a new profiling method for IRI, which is practical in computations and compatible with traditional profiling for roughness of a road-surface. The modern technology employs elaborated sensors such as gyro sensor, Global Positioning System (GPS), magnetometer sensor,?and?accelerometer to measure high-speed longitudinal motions, resulting in time series of big-data expressed as compressed longitudinal spikes. The time series of longitudinal spikes obtained from high-speed longitudinal motions are traditionally considered as a background noise for constructing a profile. The conventional IRI is calculated from big-data of the road profile by employing statistical method, but the Lagrangian model dynamically determines the road profile. The useful concept and relation among the road-roughness function?, associated roughness index (ARI), acceleration and position are introduced and examined in the present paper. The associated roughness index (ARI) defined by the current dynamical approach is examined by applying virtual simulations which represent roughness of a road-surface. The current theoretical model supports and compensates information of interpreting a profile of IRI and elucidates physical meanings for the roughness index of a road-surface.
文摘机电馈能悬挂系统是一种新型悬挂系统,在实现装甲车辆车身减振同时回收地面传递给车身的振动能量。根据摆臂式机电馈能悬挂系统工作原理,建立了相应数学物理模型,基于Adams和AMEsim搭建了减振系统与馈能系统联合仿真模型,分析了行星变速器传动比、电池电阻和扭转缓冲器刚度对系统阻尼特性和馈能性能的影响。结果表明:在车速为45 km/h的铺面路、戈壁路、起伏路、砂石路4种路面工况下,车身加速度均方根值平均为4.11 m/s 2,平均馈能功率为1411.57 W,机电馈能悬挂系统有良好的减振性能和可观的馈能功率;随着行星变速器传动比增大,悬挂系统阻尼力矩和馈能功率逐渐增大,且影响显著;随着电池电阻增加,阻尼力矩和馈能功率逐渐降低;扭转缓冲器刚度变化对悬挂系统性能影响较小。
